a) Field of the Invention
The invention is directed to a laser slit lamp with a laser radiation source and relates to the field of ophthalmology for diagnostic and therapeutic applications. Slit lamps with laser applicators are used in this field particularly for treatments of the retina such as panretinal photocoagulation in diabetic retinopathy, retinal welding in retinal detachment, grid coagulation of the retina in age-related macular degeneration (AMD) and for glaucoma treatments, e.g., trabeculoplasty in chronic glaucoma or iridotomy in acute glaucoma.
b) Description of the Related Art
Special laser slit lamps or diagnostic slit lamps with special link systems or applicators from many different manufacturers which are connected by a light-conducting fiber arrangement to an external (remote) laser radiation source generating a working beam and/or target beam are known in the art and are commercially available. Such laser slit lamps or link systems for diagnostic slit lamps are also described in the patent literature and other literature, for example, in U.S. Pat. No. 5,921,981. Combinations of a diode laser with a slit lamp or of an Nd:YAG laser with a slit lamp are known in this connection.
The usable wavelengths of laser radiation are in the near infrared and visible spectral region. Optical zoom systems are used in the optical outfitting of the applicator for adjusting the treatment spot sizes. Pulsed operation of the working radiation sources by means of intensity modulation of the pump source or by mechanical modulation (shutter mechanisms) is also known.
The extensive space requirement for the external laser source and the beam losses occurring on the path from the radiation source, via the slit lamp with the applicator, to the eye of the patent have proven to be substantial disadvantages in known combinations of external lasers and slit lamps. In order to overcome this disadvantage, it is necessary to compensate for the transfer losses by means of higher optical and electrical source powers. Other disadvantages include the high number of electric connection lines between the laser radiation source and the applying system, high setup costs, and light transfer via a sensitive light-conducting fiber to the applying system (laser slit lamp or link system).
It is the object of the invention to provide a laser slit lamp which extensively overcomes the disadvantages of the prior art and which provides a compact therapeutic and diagnostic device for medical laser applications in the field of ophthalmology.
According to the invention, this object is met in a laser slit lamp according to the preamble of the first patent claim by the characterizing means shown in this claim. Details and other constructions of the invention are described in the subclaims. The installation of a very compact diode-supported laser radiation source, including supply and control arrangements, in a slit lamp is particularly advantageous. A continuous and/or pulsed diode-pumped solid state laser, a fiber laser, a microchip laser or a diode laser, for example, can be used as the laser radiation source. The use of semiconductor laser diodes as a marking source, pumping source or treatment source ensures low electrical and optical losses. The device therefore operates very efficaciously with high efficiency. Because of this, special measures for cooling and heat dissipation can be dispensed with.
Accordingly, it is advantageous when the internal laser radiation source is a compact diode-pumped frequency-doubled solid state laser which is arranged, together with the pump light source and a nonlinear doubler crystal, in the slip lamp head, in the applicator or in the slit lamp microscope, the nonlinear crystal being arranged inside or outside the laser cavity.
It is also advantageous when Nd:YAG crystals, Nd:YVO4 crystals or Nd:YLF crystals are provided as laser materials for the laser radiation source and the light emission is carried out on the fundamental wavelength at 1064 nm, 1053 nm or 1047 nm. The frequency-doubled working radiation source emits at a wavelength of 532 nm, 562.5 nm or 523.5 nm with output powers of up to about 3 W. The wavelength of the pump radiation is in the range of 790 nm to 815 nm.
In an advantageous arrangement, the laser crystal can be connected in a known manner with the pump radiation source by a passive optical coupling element. This coupling element can be realized, for example, by means of a light guide with imaging optics.
According to another embodiment form, an up-conversion fiber laser is provided as internal laser radiation source, its active fiber laser core is Pr/Yb-doped and the emission wavelength of the working beam is 520 nm to 540 nm or 630 nm to 640 nm with output powers of up to 2.5 W. The pump radiation source can be arranged in the slit lamp base and the wavelength of the pump radiation is preferably in the range of 830 nm to 850 nm. In this case, the pump radiation source is advantageously connected with the fiber by coupling optics for coupling the pump radiation output into the active fiber core.
Another favorable arrangement results when an up-conversion fiber laser whose active fiber core is erbium-doped and whose laser emission has an output power of up to 2.5 W is provided as an internal laser radiation source. The wavelength of the laser radiation is 547 nm. The wavelength of the pump radiation is in the range of 970 nm to 980 nm and the pump radiation source is connected with the fiber by coupling optics for coupling the pump radiation output into the active fiber core.
It is also advantageous when the internal laser radiation source is an externally frequency-doubled fiber laser whose fiber core is neodymium-doped, wherein the fundamental wavelength is in the range of 1060 nm to 1080 nm and the wavelength of the working beam at output powers of up to about 2.5 W is in the range of 530 nm to 540 mm, and when poled or unpoled nonlinear optical crystals are provided for doubling, the wavelength of the pump radiation is in the range of 800 nm to 820 nm and the pump radiation source is provided with coupling optics which make possible an effective coupling of the pump radiation into the active fiber core.
An intracavity frequency-doubled fiber laser with a neodymium-doped fiber laser core can also be provided as an internal laser radiation source and a nonlinear optical crystal can be provided for frequency doubling, wherein the fundamental wavelength is in the range of 1060 nm to 1080 nm and the frequency-doubled emission wavelength of the working beam at an output power of up to 2.5 W is 530 nm to 540 nm.
Further, is it advantageous when a radiation source generating the target beam or marking beam is arranged in the slit lamp head or in the slit lamp microscope.
The pump radiation source can advantageously be a diode laser which is arranged in the slit lamp base or in the slit lamp head and whose pump radiation has a wavelength in the range of 800 nm to 820 nm, the pump diode being provided with coupling optics for effective coupling of the pump radiation into the active fiber core.
The target beam or marking beam is coupled collinearly into the working beam in a simple manner by a dichroic mirror or by polarizing elements.
Further, it is advantageous that at least one light-conducting fiber connection is provided at the slit lamp base, at the slit lamp head or at the slit lamp microscope for connecting external applicators, for example, endoprobes or head ophthalmoscopes.
A compact therapeutic laser instrument is realized by the laser slit lamp according to the invention. In particular, optical coupling losses are also reduced by the arrangement of internal radiation sources. Further, expenditure on cables is reduced considerably. A very low setup cost and small space requirement are achieved by eliminating optical transfer between a radiation source which is arranged remote from the slit lamp and the applying slit lamp. It is also possible to connect alternative applicators.
There are three basic possibilities for the arrangement of the laser radiation source, namely, the arrangement of the laser source in the slit lamp head, in the slit lamp microscope or in the slit lamp base.
The pump source can be located directly at the working beam source or in another part of the laser slit lamp. Electronics for control, regulation, monitoring and supply are advantageously located in the base of the laser slit lamp. The power supply part of the laser slit lamp can be arranged in the slit lamp base as well as externally. Higher transport voltages are advantageously used in order to ensure the transport of the electric power through highly flexible lines with a small cross section. A voltage-current conversion is then carried out in the immediate vicinity of the electric consumers (laser diodes, thermoelectric coolers, etc.).
Accordingly, the invention has the following advantages:                a compact therapeutic laser instrument is achieved;        optical coupling losses are reduced, i.e., greater efficiency, reduced initial costs and operating costs as a result of lower system powers;        low-maintenance due to compact closed assembles;        external radiation source with extensive cable is eliminated;        optical transfer between the radiation source and the applying slit lamp is eliminated;        very low setup costs and small space requirement;        possibility of connecting other alternative applicators to the laser slit lamp.        
The invention will be described more fully in the following with reference to an embodiment example.